1. Field of the Invention
This invention relates to an optical system of a camera having an automatic focusing device and more particularly to an improvement on a display system thereof.
2. Description of the Prior Art
Heretofore many automatic focusing cameras having optical systems with varied kinds of automatic focusing devices have been proposed and put into practice. It is significant for the cameras of this type to be provided with some display device that enables the user of the camera to confirm the focusing state of the lens. In an automatic focusing type single-lens reflex camera adapted for use of interchangeable lenses, the automatic focusing device becomes incapable of performing lens control in cases where an interchangeable lens having no interlocking relation to the automatic focusing device or where a quicker focusing action is necessary for a moving object. In such cases, a manual focusing operation should be performed while observing the focusing state of the lens by the air of such a display device. It is therefore desirable, against such occurrences, to have the above stated display device arranged to be capable of displaying the focusing state of the lens independently of the automatic focusing device.
The prior art cameras of the type having such a combination of an automatic focusing device and a display device include a camera in which, as disclosed in Japanese Laid-Open Patent Application No. Sho 50-99739, an automatic focuisng device is arranged to make the focal point of a photo-taking lens unvarying irrespectively of changes in object's distance after the lens is focused on the object to be photographed, so that a picture having the object in focus can be taken even when the object is positioned away from the middle portion of the picture which is an automatic focus detectable area. In that instance, however, if the display device is arranged to be operatable independently of the automatic focusing device the display by the display device would follow with fidelity the changes in the focusing state of the lens resulting from variations of distance to the object. This would not only confuse the eyesight but also tend to cause the user to miss a good shutter operating chance because the end of the focus adjusting action on the lens by the automatic focusing device is not clearly discernible due to the varying display by the display device.